The use of trays for holding impression material to make impressions of teeth and other areas of a patient's oral cavity are well known. During the impression-taking process, trays are filled with dental impression material which is then impressed onto several of the patient's teeth or against the entire upper or lower dental arch. To ensure a complete impression, it is essential that an excessive amount of impression material be used. While the tray and impression material are held in place, the material cures, and after curing the tray and material are removed from the mouth as a unit. The resulting impression is then used as a casting mold to form a model of the patient's teeth.
Trays used for taking impressions of the upper dental arch generally include a "U"-shaped trough to conform to the natural configuration of the dental arch. An area in the middle of the "U" generally includes an upward-extending pocket beneath an arched shelf to conform to the general shape of the patient's palate. This configuration is, in general, universally employed in the prior art.
A problem exists, however, in such a tightly fitting upper arch impression tray because the expulsion of the essential excess material is extremely uncomfortable for the patient. With the prior art configuration described above, the excess impression material is expelled backward into the throat area of the patient causing a gag reflex reaction which is extremely uncomfortable. There is, therefore, a need in the art for a new and improved impression tray which provides for the expulsion of excess impression material without gagging the patient.